Various types of upward acting doors include electric motor driven operators for opening and closing the door. Certain types of upward acting doors, such as flexible curtain rolling doors, are advantageously controlled by operators which include an electric motor drive unit for a rotatable drum on which the flexible curtain is wound and unwound. The motor drive unit typically includes a releaseable electromechanical brake which is engaged when the motor is deengergized to prevent unwanted rotation of the curtain drum.
However, in the event of unwanted loss of electrical power to the motor, it is desirable to be able to manually open or close the door. In this regard, the aforementioned type of motor drive unit includes a drive shaft with an external drive member which may be engaged by a manual tool to rotate the output shaft of the motor drive unit and the aforementioned curtain drum, for example. The type of motor drive unit mentioned herein also, typically, includes a manual brake release lever or mechanism which may be actuated to permit rotation of the motor output shaft.
A problem arises with the use of the aforementioned type of motor drive unit in certain upward acting door applications wherein the motor drive unit is mounted at a substantial elevation above the floor of the building at which the door is mounted, thereby rendering manual operation of the brake release mechanism and the motor drive shaft difficult. The present invention provides a solution to the aforementioned problem which is advantageous and desirable.